What occurs during the process of inspiration?

During the process of inspiration, the diaphragm contracts, which is critical for the mechanics of breathing. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity (intrathoracic space). This decrease in pressure within the thoracic cavity compared to the outside atmosphere allows air to flow into the lungs.

The interplay of muscle contraction and volume changes is fundamental to understanding respiratory physiology. In addition to the diaphragm, intercostal muscles also assist by elevating the rib cage, further contributing to the expansion of the thoracic cavity. This coordinated action effectively draws air into the lungs, which is essential for gas exchange and oxygen delivery to the body's tissues.

Therefore, the correct answer highlights the fundamental mechanics of breathing during the inspiration phase, emphasizing the role of diaphragm contraction and the resulting changes in thoracic volume. This contrasts with other options that describe processes not involved in the act of inhalation.